#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

typedef struct
{
    int greutate, valoare;
} obiect;

int fcmpq(const void *a, const void *b)
{
    obiect *A = (obiect *)a;
    obiect *B = (obiect *)b;
    double eff1 = 1.0 * A->valoare / A->greutate - 1.0 * B->valoare / B->greutate;
    // printf("%d %d\n", A->greutate, A->valoare);
    // printf("%d %d\n", B->greutate, B->valoare);
    return -(int)eff1 * 100;
}

int main()
{
    FILE *fin = fopen("rucsac.in", "r");
    FILE *fout = fopen("rucsac.out", "w");
    int n = 0, Gmax = 0;
    obiect *O = (obiect *)calloc(n, sizeof(obiect));
    fscanf(fin, "%d%d", &n, &Gmax);
    for (int i = 0; i < n; ++i)
        fscanf(fin, "%d%d", &O[i].greutate, &O[i].valoare);

    qsort(O, n, sizeof(obiect), fcmpq);

    int G = 0;
    double V = 0;
    for (int i = 0; i < n; i++)
    {
        if (G + O[i].greutate <= Gmax)
        {
            G += O[i].greutate;
            V += O[i].valoare;
        }
        else if (Gmax > G)
        {
            double x = 1.0 * (Gmax - G) / O[i].greutate;
            G = Gmax;
            V += x * O[i].valoare;
        }
        else
            i = n + 5;
    }
       fprintf(fout, "%lf", V);
    // printf("%lf", V);
    return 0;
}